Re: Doepfer A-100 Modular

From Mark Kolmar
Sent Sat, Apr 22nd 1995, 01:41

On Fri, 21 Apr 1995, Marc Mcnulty (MUSIC) wrote:

> On Fri, 21 Apr 1995, Mark Kolmar wrote:
> One problem with the PAIA kits is that the modules are based on Curtis 
> chips which are no longer manufactured.  This could be a problem in the 
> future if a module fails or you wish to expand. 

I will definitely want to expand.  Other than the possibility that Paia
just has a big box full of these out-of-production chips, why the
built-in, immediate obsolescence?  This is not encouraging.

> > (For example, I used a very modest modular at the U of Ill.  We weren't
> > really supposed to do stuff like this, but I plugged a bass guitar into 
> > at least one of the CV inputs.  It worked great.  Was I just lucky or can 
> > you do that kind of thing without worry and expect it to work?)
> Of course it will work, because the pickups of the Bass make a small 
> voltage, which is read by the CV input as a control voltage.  You can use
> mics, tape, etc. (but only use line level input, no amping) 

That I knew already or I wouldn't have done it ;-) What I'm concerned
about is that small voltage being too much to handle or too little to

Another issue has to do with different voltage standards.  One example... 
I'll guess a VCA typically behaves this way:  0V CV in = infinite
resistance, (x)V CV in = unity gain, (y)dB attenuation per (z) reduction
in voltage.  If the values of x,y, and z are different from one mfr to
another, then you'd need appropriate EGs as well.  I shudder to think what
you're going to say about CV vs. pitch from one VCO to the next.

> > A good volume of mail on this list seems to be people asking "how to I
> > drive my XXX with my YYY..."  Although these questions mostly seem to do 
> > with sequencing.  I'll need good MIDI to CV (incl. velocity and hopefully 
> > controllers).
> You will need an analog sequencer or the PAIA cv/Midi converter works 
> very well.

That's just the thing:  I didn't see a MIDI/CV in the Paia catalog except 
built into the FatMan.  The FatMan would be a good start if:

a) I can re-engineer it to be freely patchable.  With enough 
documentation this should be very do-able.

b) VCOs did more than just ramp.

c) Other (filter) envelope were also ADSR

d) HP/LP/BP VCF, not just LP.

e) Probably something else I'm forgetting.

> > - Potential hazards while experimenting with feedback loops
> Feedback loops can generate voltages beyond +5/-5v (the loops need to be
> controlled (buffered).

By this, do you just mean you need something either to max-out (e.g. 
distortion pedal=clipping amp) or to otherwise attenuate the signal (e.g.
mixer=resistor)?  To me this is a given, but good advice nonetheless.